Christopher Brimley updated October 11, 2011


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  • Backwoods Gravel Producer

    by Sam Swanson

    Photos by the author

    A busy summer day at the gravel producer. Newly crushed ballast has just been loaded onto the MOW flat, and gravel has been placed into the Ford pickup thats parked under the bunker.
    Model Railroading - February 2002 - Page 32

    As cars and trucks became popular in the first part of the 20th century, small gravel producers sprang up near new road construction projects. Many of these gravel facilities had a home-built look, and appeared as though they could be broken down for easy relocation. The components common to most facilities included a gravel storage bunker, sorting screen, bucket conveyor, rock crusher and drive mechanism. This article summarizes the construction and finishing techniques I used to scratchbuild a 1930s freelanced, backwoods gravel facility.

    Features from several gravel bunker and crusher prototypes were combined to configure my HO scale model. Although the prototypes I had as examples were served exclusively by truck, I couldn't resist placing the bunker on a narrow gauge spur, so that gons and flatcars could be used for bulk gravel and ballast shipments. Justifying rail service was rather easy, as the spur also serves Wyatt Bros. coal mine, the owner of the gravel facility. So when summer coal shipments decline, gravel shipments would be on the upswing.

    I built the model in a series of subassemblies and then combined them on a scenicked base made from extruded polystyrene foam insulation. The recommended scale lumber basswood, cardstock, and other materials required to assemble the model shown on the drawings are listed in the Bill of Materials. And what follows is the general sequence of construction, along with specific weathering and painting techniques, for each subassembly.

    Bunker and Screen

    Using the template, start by framing two bunker sides with weathered basswood. The sequence I used to prepare the wood for a moderately weathered appearance included staining, sanding, distressing, and restaining after assembly. For a light gray sheen, add three drops of India ink to an ounce of isopropyl alcohol for the wood stain. Sand with an emery board to lighten the gray, and use a sharp hobby knife to distress (woodgrain) the wood pieces.

    Assemble the seven floor trusses and yellow-glue them into place. You may find it easier to add some foam or wood blocks for foundation stones or cut all the side frame columns an equal length (each of which will level the frame). Add the tie rods, and then sheath both sides of the sloped floor. Sheath the four exterior walls, followed by three interior walls. Theres a good bit of flexibility in arranging the interior sheathing, so build a cardstock mockup first. I decided to have four slide gates (three rail side and one in back) along with an under-bunker gate. And because I modeled the side-feed bins full, the walls were built solid with gate details applied directly on the exterior side walls.

    Photocopies of Good Roads magazine articles were used as references for the crusher, bunker and conveyor. The crusher and bunker were built over graph paper sketches.
    Model Railroading - February 2002 - Page 33

    Add the wood and angle iron gate frame first and then the cardstock slide plate. I used index cards that were prepainted Floquil Black, then cut, assembled with yellow g lue, and hardened along the edges with a thin application of instant glue (usually Zap-a-Gap). Finishing is a simple matter of drybrushing rust colors (Floquil Roof Brown and Reefer Orange), ink staining and dusting with rust-colored chalk. Complete the slide gates by adding the associated levers and nut-bolt-washer (NBW) castings.

    Finish up the bunker by installing the loading chutes, catwalk and gravel. Build the chutes from cardstock and finish similar to the gates. I assembled the chutes completely (with brass wire shafts and basswood end supports), and yellow-glued each into place. Then I built the catwalk below the chutes. Pile gravel in the bunker to suit your taste, but take care when using diluted white glue to secure the piles. I used a brush to transfer a wetting agent (isopropyl alcohol) first, followed by just enough glue solution to hold the gravel in place.

    Build the screen as a separate subassembly, so that it can be positioned after the conveyor and crusher components have been attached to a base. Cut a rectangle of brass mesh, paint it black and frame it with stripwood. Then drybrush the screens top face with Rub'n Buff Silver Leaf to show wear resulting from cascading stones. Install the support legs, bracing and NBW castings. Then cut a cardstock rectangle for the screens bypass plate, finish it similar to the bunker gates, and glue it into place (open or closed, the former on my model). This plate allows the screen to act as a slide to fill the front bunker bins directly with material. And depending upon your internal bin arrangement, you may want some top-of-screen diversion plates or boards.

    Bucket Conveyor

    Assembling the conveyor will be a test of your patience. Start with the angle iron frame and end rollers, which can be made from basswood structural shapes and styrene tube. Paint this subassembly before installing the intermediate rollers and conveyor belt. You may have to sand and repaint the wood parts once to obtain a metal appearance. Use black for the frame and drybrush with silver and rust, along with a wash of ink stain. For the conveyors belt, paint typing paper Floquil Grimy Black first, then drybrush with dark gray for color variation. White glue the belt to the rollers so that there is a small overlap and the seam is on the underside of the lower end roller.

    Build the buckets from graph paper, whiteglued together and hardened with instant glue. Paint and silver the buckets similar to the screen finishing. A total of about 40 buckets are required, depending upon their final spacing along the belt. Start gluing buckets to the belt at the top roller, down along the belt top, and finish on the underside. The wood frame that supports the conveyor will vary based on your installation. My model conveyor has a relatively low angle of inclination, but some prototype bucket conveyors were installed fairly close to vertical orientation. The wood frame should be below the metal frame, and angled to clear the buckets. Use wood block spacers between the two frames. I used metalized paper rectangles and NBW castings to represents clamps holding the metal frame to the block spacers.

    Epoxy brass wire shafts into the upper and lower rollers, and add the two chain pulleys and belt pulley. A convenient way to make the belt pulley is to stack and cement two handwheels together. Paint the spokes and rim dark gray, and silver the pulley face with Rub'n Buff Silver. Build the conveyor chain from fiberglass window screen by cutting a single row of squares in half and after offsetting them, reattaching with instant glue.

    Silver the chain with Rub'n Buff, and wash with acrylic black for a metallic look. I used yellow glue to tack the chain between the upper and lower chain pulleys with a catenary shape matching the conveyors final angle of inclination. After it looked right, I touched the pulley/chain intersections with a drop of instant glue to permanently secure the chain into place. Any shiny spots were touched up with Testors Dullcote. Put the bucket conveyor subassembly aside until the crusher is finished.

    Rock Crusher

    I built the rock crusher from a variety of wood and styrene shapes mostly from my scrap boxes. I sketched the side and top outline of the crusher on graph paper, and repeatedly added/sanded material until the overall shape of the body was developed. The shapes were yellow-glued together and then reinforced with instant glue before sanding. Finer detail was added, including braces, NBW castings, and brass shafts for the flywheels and belt pulley.

    Overhead view of the rock crushing operation, including the invoice signoff between gravel plant foreman Roderick Bearing and truck driving teamster Manuel Leggs. To the left of the crusher is a stone boat, where rocks are unloaded and broken up prior to being crushed into gravel and ballast.
    Model Railroading - February 2002 - Page 34 Model Railroading - February 2002 - Page 35

    Convert two Grandt Line styrene sheaves into the flywheels. Fill the edge groove with putty to make a solid flywheel rim before painting to match the color of the body. I used a cast-metal belt pulley from a Rio Grande Models assortment, but any similarly sized casting (about 2' 9" diameter) will work. Paint the crusher body and components, and weather them heavily for accumulations of dust and grit. I used Floquil Roof Brown for a base color, and then drybrushed all surfaces with Polly Scale Aged Concrete. Weathering included dustings of rust and brown chalk, several washes of ink stains, and a final dusting of clay soil and rocks (the latter placed over small pools of brushed-on diluted white glue).

    Finish this subassembly by building the crushers feed platform and skid above and below the crusher body (after the flywheels have been attached). Then plan and construct the skid cribbing, access ramp, ladder or stairway, as your installation requires. I built these in place after the initial base scenicking was completed. Its a rather tedious approach, but the individualized look your model will have is worth the effort.

    Boiler and Drive

    Woodland Scenics makes fine skid-mounted vertical boiler and cylinder drive metal castings that are well proportioned for this sized facility. I scratchbuilt a wood skid for the boiler/drive, but the kit comes with one. The scratchbuilt version is slightly larger than the kits metal skid, which isn't as crisp as the other two castings. Cut off the pulley shaft from the cylinder body, and add a short brass shaft (about 1/8" long).

    After priming with Floquil, I painted the boiler and drive Floquil Weathered Black, washed them with a black-blue enamel stain, and silvered the piping with Rubn Buff. Several washes of ink stain over both castings, and dusting with black chalk around the boilers firebox yielded a sooty appearance. Attach the two metal castings to the wood skid with two-part, five-minute epoxy. Add the cone belt pulley by epoxying it to the brass staff. I reduced a five-cone Rio Grande Models metal casting pulley to three cones, but one could easily be built from s tacking various diameters of styrene or wood dowels (each with a scale 6" width).

    Diorama Base

    The bunker, conveyor, and drive skid can be arranged in a wide variety of configurations. I opted for an outcropping installation with a good bit of elevation difference. The diorama base was built up from extruded foam insulation and scenicked to match the scenery scheme used on my home layout.

    To maintain accessibility for detailing and in-place assembly, it's important to coordinate base scenicking with the sequence of subassembly installation. After deter mining the smallest possible diorama footprint, I located the bunker and crusher, and then carved/finished the rock outcropping. The conveyor and screen where then glued between the crusher and bunker, and the road under and around the bunker was finished with fine clay soil held in place with diluted white glue.

    After the drive skid was secured with epoxy, the crusher and conveyor drive belts were installed. Prepaint typing paper Floquil Grimy Black and drybrush with Polly Scale Earth after cutting at least two belts of each width (scale 4" wide for the conveyor and 6" wide for the crusher). Only one of each width is required, but you may want to practice with one first (a hint from someone that hasn't had much luck installing model belts). Secure the belt with yellow glue to the respective pulleys so that the short overlapping seam is on the bottom of the cone pulley. Brush on a thin coat of Dullcote once you're happy with the belt alignment and the glue holding each is fully dry.


    After the subassemblies were installed, details were added along with scenery items. The access items (ramps, stairs and ladder) were added first to complete the gravel plant. The coal skid was built from basswood and holds a load of egg-sized coal (2"-5" chunks) for the vertical boiler. The truck below the bunker is a Jordan 1929 Model AA Ford tank truck kit, with a scratchbuilt wood hauling bed instead of the tank. And the two men near the bunker are styrene figures with some added detail (papers, clipboard and pencil) in a mini-scene featuring a gravel load sign-off. Some tools and planks were added about, as were some gravel piles.

    The gravel producer diorama was worked into a larger scene, also shaped from layers of extruded foam. This is the drive side of the gravel facility. Note that the two leather drive belts are fairly taught, but the conveyor drive chain has the typical catenary sag.
    Model Railroading - February 2002 - Page 36

    On the hill, a stone boat (used as a deck for reducing rock size) was glued into place. After the scenic details (weeds, brush and trees) were added, I weathered the conveyor and surrounding area in the same fashion as the crusher for a well-used and dusty look.


    The trade publication Good Roads magazine supplied all of the information I needed for this modeling project. The specific issues that influenced my model included an article on rock crushers and several photos of crushing plants:

    • Development of the Rock Crusher - II by Willard W. Bacon (April 1905)
    • Kennett Township Crushing Plant (March 1903) 
    • Hudson NY Crushing Plant (Dec 1903) 
    • Killingly CT Crushing Plant (June 1904) 
    • Morrillton AR Crushing Plant (April 1905) 
    • Austin-Western Portable Crushing Plant (August 1928)

    Another good source of information is a Sept/Oct 1984 Narrow Gauge Gazette article by John Hitzeman on how to scratchbuild a crusher in HO scale. It was written as part of his series on ore processing. The article is well done, and I would have followed it had I not already built my crusher before finding it.

    Although this gravel producing operation is for the first third of the 20th century, there are gravel and aggregate crushing operations that persist today. The materials are all steel and the scope significantly larger though, but either eras facility would make an interesting industry on your layout.

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  • Paul Weber likes this
  • Paul Weber
    Paul Weber Good one, Chris! I might want to try this on my layout!
    December 13, 2011